Telephonic unit



Sept. 24, 1940. G, B, ELUS .2,215,782-

'rEEPHoNIc UNIT Filed Aug. 31, 1938 5 vShawna-Sheet. l

/W ATTORNEYS Sept. 24, 1940. G. B. ELLIS 2,215,782

TELEPHONIC UNIT Filed Aug. 31. 1938 5 Sheets-Sheet 2 39 lam 911 MMM i l im Z .4 72 lNvENTO R fj? MJWAM? Sept. 24, 1940. G. B..ELL|s 2,215,782

TELEPHONIG UNIT Filed Aug. 3l. 1938 5 Sheets-Sheet 3 Patented Sept. 24, 1940 UNTED STATES rarest ortica TELEEHONC UNIT Grenville' EB. Ttlis, Brooklyn, N. Y., assigner to Jontroi instrument Company inc., Brookiyn, N. Y., corporation oi York .ppiication August 3l, 1.938, Seriai No, 223,65@

ple, the unit may be connected with a car'oontransmitter `on a line energized by batteries or other source of current, at which time the unit operates as a receiver. The device is especially designed. however, for military use wherein it is important that simplicity and rigidity of parts be 'considered in the construction and operation oi the device, and to this end, the device is designed to operate emciently in a simple electric circuit with a unit on each end of the circuit and without additional electrical'apparatus.

More especially, the construction is such that accurate assembly is accomplished through the design of intertting parts which automatically maintain desired constants when the device is assembled. The elimination of disturbing Foucault currents is attained and the parts of the device are so shaped and arranged as to avoid blasting under excessive sound conditions which frequently occur in the use of military telephones, either in the Navy or Army, where telephones are often installed in the proximity of big guns. The discharge of heavy pieces of ordnance sets up very violent sound waves and air waves which may destroy the effective operation of ordinary telephonic apparatus. The present invention comprises a construction which operates efficiently even in the proximity of large guns which are firing.

Other and further objects of the present invention will in part be obvious and will in part be pointed out hereinafter by reference to the accompanying drawings forming a part of this application and throughout which like characters,

are used to represent like parts.

Fig. i is a plan View of the preferred embodi- Fig. 4 is a side elevation similar to Fig. 1 withy the permanent magnets removed and the energizing coil in section and with other portions o the construction in section.

Fig. 5 is a sectional View taken on line 5 5 oi Fig. i but showing the permanent magnets in place and in section. v v o Fig. 6 is an exploded view of the, coil, the armature, the pole pieces, and certain assembly parts.

Fig. 7 is a diagrammatic view illustrating the path of the magnetic lines oi force through certain ci the pole pieces.. g

Referring to the drawings, a preferred embodiment of the present invent-ion comprises a clrcular oase member l upon and Within which the operating elements-oi the unit are mounted. A base i is provided with a recess 2 in whichis mounted l5 a diaphragm d. This diaphragm is held in place by being seated upon a shoulder 5 in the base plate l and is clamped in position against thcxv shoulder by means of a clamp ring 6 which bears against a non-rotatable ring 'I that rests on the zo edge of the diaphragm. The base plate I is provided with a plurality of openings 8 to obviate the iormation oi a dead air pocket back of the diaphragm.

Brass mounting screws 9 and I0 are screw 25 threaded into tapped openings in the base member l and these mounting lscrews 9 and I0 comprise the setting members around which the assembly of the unit is based. A pair of pole pieces II and I2 are formed from stampings of soft non- 30 corrosive sheet steel which are tightly riveted together by hollow brass rivets I4 to form laminated structures providing a suitable path for magnetic lines of force. Brass channel strips I5 and i8, identical in form, are provided with ears 35 Il which have openings therein through which the brass mounting screws 9 and I0 extend. -The sides I8 and I9 of the brass channels I5 and i6 are adapted to embrace and hold the endsof the pole pieces II and i2. A voice coil 20 is assembled 40 on the lower pole piece I2 by telescoping the notches 2l in the side walls oi' the coil spool I3 over the bar of the pole piece I2 so that the coil ts between the legs 22 and 24 of the pole piece I2. An armature 25 of hard. Armco" silicon 45 sheet steel is extended4 through an opening 26 in the spool I3 of the coil 20 and a pair of brass f shims 21 and 28 together with the fixed end of the armature are extended through an opening 29 in the channel strip I5. The width of the arma- 60 ture 25 andthe brass shims 21 and 28 is such as to contact the sides I8 and I9 of the brass channel strip I5 and are also provided with openings through which the brass mounting screw 9 extends. This construction is such that when the 66 armature zu and the brass shims :1 and 2s, so

that the co-planar pole faces ll, l2, and I4 of the pole piece I2 are all automatically spaced equal distances from the co-planar pole faces 25, Il. and I1 on the pole II vwhen the pole piece II is assembled within the sides Il and Il of the channel strips I5 and I6 and over the notches Il in the lupper side of the spool Il for the voice coil 20.

A mild steel top plate Il bears upon the top oi the pole piece I I and is provided with openings 40 and 4I through which the brass mounting screws 9 and I0 extend. This top plate is slightly bowed, with the convexity of the plate being upward, so that when the mounting screws B and I0 are screwed into the base member I. the top plate I8 is straightened out and applies a downward force on the pole piece II, the spacer block 30, the shims 21, 25, the fixed end of the armaturc 25, and on the pole piece I2. A terminal block 42 of insulating material is secured by a rivet 44 to the forward end of the top plate Il and is provided on its ends with terminals 45 and 48 to which the ends 41 and 45 of the voice coil wire are respectively attached. A light weight stiif strut rod 49 adjustably connects the free end of the armature 25 with the diaphragm 4 and this rod 48 extends through an opening 50 provided throughthe pole piece I2 (Fig. 4), and one of the openings l in the base member I.

From the foregoing. it will be observed that the construction and assembly of the unit comprising the present invention is of simplified design and the brass mounting screws l and I0 are the major frame work on which the assembly is predicated so that by passing these screws through the openings provided in the ears I1 of the channel strips, the shims, the spacing block. and the armature with the voice coil in place between the pole pieces. and the top plate in position, the parts are precisely, positively, and definitely assembled in correct relation. Thus after the parts are fabricated. the major assembly is accomplished by the setting of the two brass mounting screws 8 and I0 in the base member I.

Permanent magnets 5I and 52 (Figs. 1, 2, 3, and 5) complete the assembly. These permanent magnets are made of high residual flux density metal comprising an aluminum, nickel, steel alloy known to the trade as Al-Ni-Co steel. These permanent magnets 5I and 52 are provided with openings 54 and 55 which enclose the voice coil 20, and the pole faces of the permanent magnets 5I and 52 are closely fitted against the sides of the pole pieces II and I2. The permanent magnets 5I and 52 are assembled with these pole pieces II and I2 in such manner that common magnetic poles are positioned on opposite sides of the respective pole pieces so that the entire pole piece II will have one magnetic pole charactcristic, and the entire other pole piece I2 will have the opposite magnetic pole characteristic, in order that the magnetic flux tends to flow between the pole faces II-I5, 22-28, and 44-21, respectively. The permanent magnets 5I and 52 are held in position by spring brackets 55 and 51 that are mounted on the base member I by means of stub screws 5I and 5l in such manner that the upstanding arms of these brackets act as springs v to push the permanent magnets toward each other and against the sides of the pole pieces II and I2. The permanent magnets 5I and l2 are further held in position by ears 5l and II that depend from the top plate Il and extend downwardly on opposite sides of the permanent magnets 5I and 52.

Referring now more especially to Fig. '1, which is more or less of a diagrammatic ligure. it will be observed that the length of the shims 21 and 2l is less than the length of the pole faces II-II, and that the brass spacer 25 extends between the pole faces I4-l1l a distance which is less than the length of these pole faces. The area of the free air space between the pole faces II-Il is indicated by the bracket C (Fig. '1) and the area of free air space between the pole faces I4 and I1 is indicated by the bracket A. The free air space area A combined with the free air space area'C, equalsl the free air space area B between the pole faces 22-55.

When "blasting" occurs, the effect is produced in the receiving unit due to the fact that anoverload or unusual heavy alternating current is effective in the system. When a gun of large caliber is ilred in the proximity of a transmitting unit, the diaphragm flexes to an unusual extent and imposes its movement on the armature which sends out into the system, through the voice coil, an alternating current having peaks of unusual magnitude. When such a current is received in the receiving unit, in accordance with the present invention, the disturbance of the electrical field produced by the armature at the receiving unit tends to vary the flux in the pole pieces II and I2. This variable flux flows between the pole faces )L -35, 32-38 and 34-31. The total variable flux effective between the pole faces II-II is diminished by the shunt flux flowing between the pole faces 2I,-l5 and $4-31. Therefore, the total variation as between the pole faces 32-35 is diminished for peak'loads and consequently, the unit does not blast to the extent that would occur in a single pole construction utilizing the pole faces 82-25 alone.

It is also recognized in the electrical arts that where a varying magnetic ilux passes through a metallic conductor, such as a piece of brass or a piece of copper, local currents are set up that are known as "Foucault currents. The magnetic flux tends to take the shortest path, and, therefore. so far as the pole faces 3I35, and 24-31 are to be considered, the flux from the permanent magnets 5I and 52 will substantially follow the dotted lines X and Y, and will concentrate adjacent the inner corners of the pole faces I I-I5, and 24-31. It is to be observed that there is no metal between these pole faces adjacent these inner corners and, therefore, the tendency to produce Foucault currents in the unit is substantially lessened. This also contributes to the effective operation of the unit. A

The above features of the present invention produce a telephonic instrument which is particularly useful for military work, and the present instrument is being used, without a battery, in the circuits over distances of many miles to transmit conversation in a completely satisfactory. audible manner.

It is to be understood that the unit comprising the present invention is mounted in a suitable casing such as a handle which is provided with the diaphragm. as is well known in the art.

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